Known infrared photodetectors include Silicon Optical Amplifiers (SOA) and Short-wave Infrared (SWIR) cameras that are made of crystalline Indium-Gallium Arsenide (InGaAs) semiconductors that are complex and expensive to manufacture. Attempts to reduce the cost of SWIR camera have been made to obtain SWIR spectral range having CMOS process compatibility.
The reference “High performance SWIR sensing form colloidal quantum dot photodiode arrays” (Ethan Klem et al., Proc. Of SPIE vol., 8868, 886806-01, 2013) discloses an attempt at direct fabrication on CMOS wafers using Lead Sulfide (PbS) colloidal quantum dots in SWIR: p-PbS/n-C60 (p-doped Lead-Sulfide on n-doped Carbon) heterojunction detectors, having at room temperature an external quantum efficiency (QE) of 21% at Vd=0V bias under 850 nm illumination of 1 mW/cm2. The dark current density was rather high at 137 nA/cm2 at −20 mV bias. Alternatively, the reference “Short-wavelength infrared photodetector on Si employing strain-induced growth of very tall InAs nanowire arrays” (W. Shin et al., Nature, 2015) discloses making Indium Arsenide (InAs) nanowires for SWIR detection but with a poor detectivity of 1e5 cmHz1/2/W and a dark current density of 1e7 nA/cm2 at 220 K.
A Bismuth Tellurium on Silicon (Bi2Te3/Si) heterojunction photodetector was disclosed in the reference “Ultra-broadband and high response of the Bi2Te3-Si heterojunction and its application as a photodetector at room temperature in harsh working environments” (J. Yao et al., Nanoscale, vol. 7, p. 1235, 2015), where the Bi2Te3 was used as a topological insulator for THz detection (see FIG. 1). Due to its low-bandgap, IR detection was feasible with detection of 1.55 μm IR, but a disadvantage of this heterojunction photodetector was its low responsivity and high dark current density. Further, this reference taught using a pulsed-laser deposition technique to form the Bi2Te3 layer.
What is urgently needed in the field of infrared detectors is an infrared (IR) photodetector that will overcome the limitations described above, and with improvements in quantum efficiency, with substantially reduced dark density and with good detectivity.